1. Field of the Invention
The present invention relates to an electrical energy storage system, such as a battery, and more particularly, a battery of the metal/halogen/hydrate type.
2. Description of the Prior Art
The electrical energy storage system utilizes a halogen hydrate as the source of a halogen component for reduction at a normally positive electrode and an oxidizable metal adapted to become oxidized at a normally negative electrode during the normal discharge of the storage system. As aqueous electrolyte is employed for replenishing the supply of the halogen component as it becomes reduced at the positive electrode. The electrolyte contains the dissolved ions of the oxidized metal and the reduced halogen and is circulated between the electrode area and a storage area containing halogen hydrate which progressively decomposes during a normal discharge of the electrical energy storage system, liberating additional elemental halogen to be consumed at the positive electrode.
Electrical energy storage systems or secondary batteries of this type are categorized as being of the so-called high energy density (H.E.D.) type since they are capable of supplying upwards of 50 watt hours of electric power per pound of weight. The high energy capacity and compactness of such H.E.D. batteries renders them particularly satisfactory for use as principal or auxiliary sources of electrical energy in both mobile and stationary power plant systems. A metal/halogen/hydrate secondary storage battery of the foregoing type is described in detail in U.S. Pat. No. 3,713,888, issued Jan. 30, 1973 entitled "Process for Electrical Energy Using Solid Halogen Hydrate", which is owned by the same assignee as the present invention. The specific teachings of the aforementioned United States patent application are incorporated herein by reference.
Among the advantages of secondary storage batteries of the metal/halogen/hydrate type is the ability of such systems to be refueled or recharged quickly and efficiently whereby they are again restored to full-charged capacity. In a refuelable secondary storage battery, the halogen constituent is replenished by withdrawing a proportion of the aqueous electrolyte and substituting therefor a halogen hydrate which, upon decomposition during normal discharge, liberates elemental halogen and water, whereby the concentration of the metal halide in the electrolyte remains substantially constant during the discharge cycle. The halogen hydrate comprises a compact and extremely convenient method of storing and replenishing the halogen component in the storage system. In a rechargeable storage battery system, a reverse electrical current is applied to the electrode area, whereby the halide is oxidized to the elemental halogen which is recovered as a gas and is reconverted in the presence of water in the corresponding halogen hydrate storage area within the system. In either event, the formation of the halogen hydrate is accomplished under controlled temperature conditions, whereby halogen and water are combined to produce a corresponding solid hydrate. This operation can be performed within the system itself or by a central hydrate processing unit disposed remote from the electrical energy storage system.
The present invention is directed to an improved apparatus and process for producing and storing halogen hydrate in an efficient and economical manner utilizing the aqueous electrolyte as a source of the water and halogen components or, alternatively, sources of these two components independent of the electrical energy storage system.